The head of the agency overseeing Boston's Big Dig highway project ordered a review of the entire metro highway system Wednesday after investigators looking into the fatal collapse of concrete ceiling slabs found 60 more questionable areas inside the same tunnel.

Initial inspections revealed dozens of signs of bolts loosening and other potential failures in the eastbound connector tunnel, part of the main route to Boston's Logan Airport, Turnpike Authority officials and the Big Dig project manager said.

There were also trouble spots in the tunnel's westbound lanes, they said.

"We're evaluating each of these individual sites," Massachusetts Turnpike Authority Chairman Matthew Amorello said. He added, however, "The tunnel system is safe."

There had been plans to reopen the connector tunnel Wednesday, but Amorello said it would remain closed indefinitely to ensure motorists' safety.

Twelve tons of concrete ceiling panels in the tunnel crashed down late Monday night, crushing a car and killing a 38-year-old woman inside. Her husband barely escaped by crawling through a window.

U.S. Attorney Michael Sullivan, whose office has been conducting a yearlong investigation into problems with the massive highway project, told The Associated Press on Wednesday that his investigators are turning their attention to whether contractors involved in that part of the system delivered the goods and services they promised.

"We obviously want to identify any public safety risks ... but also to ensure that what the government paid for — through tax dollars — is in fact what was delivered," Sullivan said.

The woman's death could also lead to charges of negligent homicide, said Massachusetts Attorney General Tom Reilly, who is treating the section of eastbound Interstate 90, near the entrance of a connector tunnel to Logan Airport, as a crime scene.

Amorello has said a steel "tieback" that held a 40-foot section of ceiling panels gave way, letting the concrete slabs loose as the car drove beneath it.

He and Michael Lewis, project director for the Big Dig, told reporters Wednesday that inspectors had also discovered some bolts were starting to come from that tunnel's concrete ceiling, and that in other locations there were gaps between the ceiling and a metal plate holding the 3-ton panels in place.

The systemwide evaluation ordered Wednesday covers the entire metro Boston highway system — roadways, bridges, tunnels and even areas that weren't part of the $14.6 billion Big Dig project.

The Big Dig, started in 1991, was the most expensive highway project in U.S. history. It buried Interstate 93 beneath downtown and extended the Massachusetts Turnpike to the airport. It also gained nationwide notoriety for its soaring costs, years of traffic snarls, the criminal investigation into the concrete suppliers and problems with leaks that sprouted in another of the Big Dig tunnels.

Sullivan's office brought the first criminal charges related to the Big Dig project in May, accusing six men who worked for its largest concrete supplier of falsifying records to hide the inferior quality concrete.

The section of tunnel ceiling that collapsed was near the entrance to the Ted Williams Tunnel, which runs under Boston Harbor to the airport. That segment of the tunnel was completed in 1995-96, but the ceiling panels were installed in 1999.

Modern Continental, the contractor of that portion of the project, issued a statement saying its work "fully complied with the plans and specifications provided by the Central Artery Tunnel Project. In addition, the work was inspected and approved by the Central Artery Tunnel Project."

Andrew Paven, a spokesman for project manager Bechtel/Parsons Brinckerhoff, said the company was working with the Turnpike Authority to pinpoint the cause and to prevent future accidents.

Angel Del Valle, 46, and his wife Milena were driving to the airport Monday night to pick up relatives when four of the slabs dropped on their car just after 11 p.m.

"It was like a bomb," Angel Del Valle, who was able to climb out a window to safety, told the Boston Herald. "Everything was falling. It was too fast. I couldn't stop. I couldn't do anything."

Milena was on the passenger side, which bore the brunt of the damage. There was no way to pry open the passenger side door, he said.

"I wanted to do the impossible," he told The Boston Globe.

Click here to read the Boston Globe story.

Debris littered the stretch of Interstate 90, which authorities hoped to reopen Wednesday. They removed about 30 ceiling slabs from the accident site and were checking at least 17 other areas with similar "tiebacks," which officials believe failed to hold the ceiling panels in place in the tunnel Monday night.

Gov. Mitt Romney pinned much of the blame on the Massachusetts Turnpike Authority and promised to take legal action to oust its chief, Matthew Amorello. He compared the situation to the replacement of former Federal Emergency Management Agency head Michael Brown after Hurricane Katrina.

"People should not have to drive through the Turnpike tunnels with their fingers crossed," said Romney, a longtime critic of Amorello.

The highway project, known formally as the Central Artery and Third Harbor Tunnel project, buried Interstate 93 beneath downtown and extended the Massachusetts Turnpike to the airport. It has gained nationwide notoriety for its soaring costs, years of traffic snarls, the criminal investigation into the concrete suppliers and problems with leaks that sprouted in another of the Big Dig tunnels.

The section that collapsed was near the entrance to the Ted Williams Tunnel, which runs under Boston Harbor to Logan International Airport. That segment of the tunnel was completed in 1995-96, but ceiling panels were installed in 1999.

Modern Continental, the contractor of that portion of the project, issued a statement that its work "fully complied with the plans and specifications provided by the Central Artery Tunnel Project. In addition, the work was inspected and approved by the Central Artery Tunnel Project."

Andrew Paven, a spokesman for project manager Bechtel/Parsons Brinckerhoff, said the company was working with the Turnpike Authority to help pinpoint the cause and to prevent future accidents.

Amorello said the tunnels are safe and said he would not step down. "We will work on all of this, together, cooperatively," he said.

"This is a horrible, horrible event," Amorello said. "It was an anomaly and we will get to the bottom of it."

He said a steel "tieback" that had held a 40-foot section of ceiling over eastbound Interstate 90 gave way, letting the concrete slabs loose. He appointed a state police major, two outside consultants and a team from the Federal Highway Administration to assist in an investigation into the cause of the collapse.

The idea for the Big Dig was conceived in the 1970s, but construction did not begin until 1991. Over the years, it has faced repeated criticism for its ballooning cost and a variety of construction problems. There have been water leaks and at least one incident when dirt and debris from an air shaft fell onto cars.

In May, prosecutors charged six current and former employees of a concrete supplier with fraud for allegedly concealing that some concrete delivered to the Big Dig was not freshly mixed. Amorello said preliminary investigation shows that the quality of the concrete was not to blame for Monday's accident.

While some drivers called the collapse a "freak accident," others said it was a horrific reminder of years of bad events surrounding the Big Dig, and wondered whether they could trust the government to fix the problems.

"From the leaks to now this," said Dominic DeRiso, 21, "it seems as though there was a lot of carelessness in the planning."